arXiv subjects

Jorge Viamontes

Publications and source records attributed to Jorge Viamontes.

3 recordsLinked to original sources

arXiv2006

The Isotropic to Nematic Liquid Crystalline Phase Transition of F-actin Varies from Continuous to First Order

We report that the properties of the isotropic to nematic liquid crystalline phase transition of F-actin depend critically on the average filament length. For average filament lengths longer than 2 $μ$m, we confirm previous findings that the phase transition is continuous in both alignment and concentration. For average filament lengths shorter than 2 $μ$m, we show for the first time a first order transition with a clear discontinuity in both alignment and concentration. Tactoidal droplets of coexisting isotropic and nematic phases, differing in concentration by approximately 30%, form over the course of hours and appear to settle into near equilibrium metastable states.

physics.bio-ph↗

arXiv2005

Formation of nematic liquid crystalline phase of F-actin varies from continuous to biphasic transition

We show that the isotropic to nematic liquid crystalline phase transition of F-actin can be either continuous or discontinuous, depending critically on the filament length. For F-actin with average filament length > 3 um, we confirm that the transition is continuous in both filament alignment and local concentration. In contrast, for filament length < 2 um the F-actin solution undergoes a first order transition. Tactoidal droplets of co-existing isotropic and nematic domains were observed. Phenomena of nucleation-and-growth and spinodal decomposition both occur, depending sensitively on the exact concentration and average filament length of F-actin. In the late stage, the tactoidal droplets continually grow and occasionally coalesce to form larger granules.

cond-mat.soft↗

arXiv2002

A continuous isotropic-nematic liquid crystalline transition of F-actin solutions

The phase transition from the isotropic (I) to nematic (N) liquid crystalline suspension of F-actin of average length $3~μ$m or above was studied by local measurements of optical birefringence and protein concentration. Both parameters were detected to be continuous in the transition region, suggesting that the I-N transition is higher than 1st order. This finding is consistent with a recent theory by Lammert, Rokhsar & Toner (PRL, 1993, 70:1650), predicting that the I-N transition may become continuous due to suppression of disclinations. Indeed, few line defects occur in the aligned phase of F-actin. Individual filaments in solutions of a few mg/ml F-actin undergo fast translational diffusion along the filament axis, whereas both lateral and rotational diffusions are suppressed.

physics.bio-ph↗